Not applicable.
Not applicable.
This invention relates generally to a computer-implemented process and apparatus for scoring supersonic aerial projectiles, and more particularly to a time-difference process and apparatus for measuring the acoustic shock waves propagated by supersonic aerial projectiles to calculate the impact points of the projectiles on a strafe target. Also determined are projectile dive angle, projectile approach heading, projectile velocity and other useful scoring data such as the number and rate of projectiles fired, the impact pattern of the projectiles, projectile caliber, and estimated strafing distance of the strafe aircraft.
This invention is directed to a time-difference process and apparatus for scoring supersonic aerial (strafe) projectiles fired at a strafe target. The process and apparatus scores each projectile by measuring, detecting and calculating the differences of the time of arrival of the acoustic shock wave propagated by the projectile at an array of transducers disposed nearby the strafe target.
The process of past scoring systems has been to sample acoustic shock waves of supersonic aerial projectiles by use of a single or pairs of acoustic transducers. These transducer(s) produce an electrical signal whose amplitude is a function of the projectile distance from the transducer and the projectile size and speed. This signal is sent to a computer-implemented scoring unit where it is scaled using fixed projectile caliber and signal threshold parameters. The scaled signal is then compared to a preset threshold level. If the signal is greater than the threshold the scoring unit assumes that the projectile passed through the strafe target and a score (e.g., a xe2x80x9chitxe2x80x9d) is registered. If the signal is lower than the threshold level, no score (e.g., a xe2x80x9cmissxe2x80x9d is registered.
The accuracies of the past scoring processes are dependent on the amplitude of the signal generated by the transducer. Any factor that adversely affects this amplitude of measuring acoustic shock waves produces inaccurate strafing scores. For instance, the use of fixed projectile caliber and signal threshold parameters produces scoring errors because projectiles have varying muzzle velocity and ballistic parameters based upon the manufacturer type and production date of the projectiles. Moreover, since commercial transducers do not have identical frequency responses, transducers matched at one frequency or projectile caliber will not match at different calibers. Transducers also degrade due to weathering and must have regular calibration performed to insure accuracy. Such calibration is typically time-consuming and expensive.
Past scoring processes do not adequately account for the adverse affect on scoring accuracy caused by the speed of the strafing aircraft or platform firing the supersonic aerial projectiles. The speed of a strafing aircraft affects the velocity of the projectile at the target, which in turn affects the amplitude of the signal produced by the transducer. Aircraft strafing at high speeds will produce greater scores than would be received at slower speeds due to the increased energy of the shock wave at the target location. Past scoring processes do not differentiate between aerial (strafe) projectiles fired from static or slow-moving platforms and projectiles fired from fast-moving platforms such as jet aircraft, even though this has a significant affect on scoring accuracy.
Moreover, in past scoring processes the firing range of a strafing aircraft must be known to accurately set the fixed projectile-caliber parameter. In field use, however, strafing aircraft firing ranges vary widely between different aircraft, different pilots of the same aircraft, and even different strafing passes of the same pilot. Scoring inaccuracies results because aircraft strafing at close range receive greater scores than would be received at farther ranges due to the increased energy of the acoustic shock wave at the strafe target.
Past scoring processes also do not adequately account for the affect of ambient weather conditions on the flight paths of the aerial projectiles and upon the acoustic shock waves propagated by the projectiles. For example, the acoustic transducers used in some prior scoring apparatus use a thermistor in their circuitry that is intended to, but does not adequately compensate for, the changes in the transducer electrical output signal caused by varying ambient atmospheric temperatures. Varying ambient atmospheric temperature, wind velocities and barometric pressures significantly affect the energy of the shock wave and flight characteristics of the aerial projectiles. These weather conditions can in turn have an adverse affect on scoring accuracy because the transducer amplitude produced can vary under identical strafing parameters. The degree to which weather conditions adversely affect system accuracy is unknown in the past scoring processes and no calculation to compensate for weather affects is used.
Past scoring processes do not indicate to an operator what region of the strafe target the aerial projectiles impacted, in what order they arrived at the strafe target for pattern analysis, or which direction the off-target projectiles went. Moreover, using past processes it is very difficult for the pilot of the strafe aircraft to accurately assess aerial projectile scoring patterns due to the typically-extreme firing distances involved and the necessity for strafing aircraft bank away from the target after firing. Spotting planes and video-based surveillance systems are sometimes used to spot such scoring patterns, but not to any degree of useful accuracy. Since the impact pattern of the aerial projectiles cannot be accurately determined using the past scoring processes, analysis of aircraft pilot technique, strafe projectiles and strafe-gun system performance, and weather (notably wind velocity) affects are not possible.
Past scoring processes are inaccurate because they use a scoring area defined by the polar detection pattern of the transducer rather than the strafe target itself. In past scoring processes, the scoring area is semi-elliptical or can be made semi-circular with the addition of a transducer xe2x80x9ccap.xe2x80x9d This non-tactical shape is essentially defined by the polar pattern of the transducer""s microphone and cannot be changed. The scoring area position is fixed by the location of the transducer and cannot be offset from it. Since the physical range target is often offset from the transducer, this offset can produce scoring errors because the strafe target can be impacted without the scoring process indicating any corresponding score.
Past scoring processes also lack printout or storage capabilities for scoring archival purposes and trend analysis. Finally, aerial projectile parameters such as the projectile dive angle, strafe aircraft firing range, and the heading angle cannot be determined by the past scoring processes.
Information relevant to attempts to address these problems can be found in:
a. U.S. Pat. No. 4,813,877 to Sanctuary, et al.
Further relevant attempts to address these problems can be found in the following printed publications:
b. EON Instrumentation, Inc., Operational and Maintenance Manual for the Remote Strafe Scoring System Model SSS-101 (1989);
c. YPG/Oehler Research, Field Acoustic Target for Yuma Proving Ground (1998);
d. Air Target Sweden AB, Miss Detection Calculator MDC-80 (1986);
e. Acoustic Detection Traces Bullet, Shell Trajectories, Signal Magazine (November 1994);
f. Building a Better Bullet, Air Force Magazine (July 1993);
g. Sniper Locator Finds Shooter Quickly, National Defense Magazine (November 1996);
h. Arcata Associates, Inc., ARCATA/ADI Air-to-Ground Scoring Systemxe2x80x94System Test Report (1995);
i. Oehler Research, Inc., Enhanced Acoustic Scoring Systemxe2x80x94Informal Report (1995); and
j. Cartwright Electronics, Executive Summary CEI-2728 Area Weapons Scoring System (1990).
Each one of these references, however, suffers from one or more of the following disadvantages:
a. U.S. Pat. No. 4,813,877 discloses a strafe scoring system that uses the aforementioned amplitude scoring process of scoring the impact points of supersonic aerial projectiles upon a strafe target. The system further requires the operator to manually input the caliber of the aerial projectile and weather information to enable the disclosed amplitude scoring process.
b. EON Instrumentation, Inc., Operational and Maintenance Manual for the Remote Strafe Scoring System Model SSS-101 (1989), discusses a system that uses a single transducer to sample supersonic projectile acoustic shock waves using the aforementioned amplitude scoring process. The EON system calculates hits or misses on a strafe target using fixed projectile caliber and signal threshold parameters and does not take into account the affect of local weather conditions on the flight paths of the aerial projectiles or their acoustic shock waves.
c. YPG/Oehler Research, Field Acoustic Target for Yuma Proving Ground (1998), discusses improvements to an existing scoring system that includes requiring the operator to manually input the caliber of the aerial projectile and weather information to enable the disclosed amplitude scoring process.
d. Air Target Sweden AB, Miss Detection Calculator MDC-80 (1986), discusses a system that calculates the time of arrival of the acoustic shock wave of an aerial projectile over two pairs of transducers sequentially interposed between the firing aircraft and a strafe target. The system estimates target impact points based on the trajectory of each projectile before as well as after passing over each set of transducers. The system does not does not take into account the speed or range of the firing aircraft or the affect of local weather conditions on the flight paths of the aerial projectiles or their acoustic shock waves.
e. Acoustic Detection Traces Bullet, Shell Trajectories, Signal Magazine (November 1994), discusses a sniper-location system that utilizes a portable suite of three piezoid crystal sensors to discern a projectile""s shock wave and extrapolate its path back to the originating weapon. The system calculates the approximate azimuth of the trajectory of each projectile passing directly over the sensors using an amplitude process, but does not indicate any scoring data or perform any scoring trend or archival functions.
f. Building a Better Bullet, Air Force Magazine (July 1993), discusses a new type of aerial projectile (strafing ammunition) introduced at military strafing ranges. This illustrates the problem with past scoring systems concerning scoring inaccuracies that may be caused by projectiles that have muzzle velocity and ballistic parameters that do match the fixed projectile caliber and signal threshold parameters programmed into the scoring system.
g. Sniper Locator Finds Shooter Quickly, National Defense Magazine (November 1996), discusses a sniper location system that uses a single transducer to determine the location of the originating weapon and projectile flight path trajectory. The system uses the aforementioned amplitude scoring process and does not perform any scoring, trend or archival functions.
h. Arcata Associates, Inc., ARCATA/ADI Air-to-Ground Scoring Systemxe2x80x94System Test Report (1995), discusses attempts to improve the accuracy of past scoring systems caused by inadequate transducer timing, transducer signal processing and the affects of weather factors on system accuracy.
i. Oehler Research, Inc., Enhanced Acoustic Scoring Systemxe2x80x94Informal Report (1995) discusses attempts to improve the accuracy of past scoring systems by experimenting with a variety of transducer arrays and iterative formulae.
j. Cartwright Electronics, Executive Summary CEI-2728 Area Weapons Scoring System (1990), discusses a detonation scoring subsystem for determining the detonation location of explosive aerial rockets fired by helicopter gunships. The system uses four transducers to sample the shock waves propagated by the rocket detonations and requires the operator to manually input the caliber of the aerial projectile (rocket). The system does not compute any projectile velocity data, nor does the system take into account the range or relative movement of the firing aircraft.
In contrast to the aforementioned references, this invention use a computer-implemented iterative algorithm to calculate the actual location of each aerial projectile impact in a strafing burst, its dive angle, heading angle, and weapon caliber, and the burst firing range and approximate firing range of the aircraft. Additionally in this invention, ambient atmospheric temperature and wind velocity are automatically measured and listed with the computed parameters, thereby providing the operator with a comprehensive set of scoring data for each strafing pass. This invention enables the operator to define scoring area shapes and sizes that may be customized to the physical strafe target, thereby improving scoring accuracy. The strafe target can be offset from the system transducers allowing the scoring area to be coincident with the physical strafe target and independent of the location of the transducer array.
The iterative algorithm process implemented by this invention utilizes the difference in arrival times of the aerial projectile shock waves between the array of transducers rather than utilizing the amplitude of the signal output of a single transducer. Eliminating the scoring dependence on the transducer signal amplitude eliminates the numerous causes of past scoring processes inaccuracies. Since the process of this invention is independent of the amplitude of the transducers"" signal outputs, the caliber and shape of aerial projectiles, differing projectile velocities, firing range, speed of the strafe aircraft, and differing transducer sensitivities will not adversely affect projectile scoring accuracy.
By calculating the differences in arrival times between at least three of the arrayed transducers, the algorithm implemented by this invention permits a computed solution of where each aerial projectile passes in relation to the transducers. The use of a second row of transducers in line with the transducer row nearest the target allows for computation of the projectile speed, dive angle, and heading angle. Further, the algorithm implemented by this invention extrapolates the firing range of the strafing aircraft by using a stored ballistic table for the projectile caliber detected by the invention.
By this invention, computed impact points are quantitatively scored as a hit or miss depending on whether they pass within the selected scoring area and shape projected onto the physical range target. Both hits (on-target) and misses (off-target) are plotted in relation to the scoring area to give an operator a visual hardcopy record of the aerial projectile scoring pattern and the sequence in which the projectiles impacted the strafe target. Finally, the projectile impact points and the computed and measured projectile data are stored in the computer memory for later scoring trend analysis.
For the foregoing reasons, there is a need for an improved computer-based time-difference process and apparatus for scoring supersonic aerial projectiles directed at a strafe target.
The present invention is directed to a computer-based process and apparatus that satisfies the need for an improved time-difference process and apparatus for scoring supersonic aerial projectiles directed at a strafe target.
A process and apparatus having features of this invention comprises an array of at least six transducers disposed proximately to a strafe target, the transducers being independently and automatically operable to transmit analog signals in response to the acoustic shock waves propagated by supersonic aerial projectiles directed at the strafe target. A multichannel signal processor is coupled to the transducers for receiving the analog signals and converting the analog signals to equivalent digital signals. The signal processor transmits the signals to at least one general-purpose digital computer coupled to the signal processor. The computer implements an iterative scoring algorithm, which measures and processes the digital signals for computing scoring data for the supersonic aerial projectiles.
In accord with one aspect of this invention, the computer implements the algorithm to determine scoring data for the supersonic aerial projectiles by measuring the time differences of arrival of the acoustic shock waves at each of the transducers, and comparing the scoring data with target data from the physical strafe target.
Preferably, the multichannel signal processor is capable of automatically triggering, sampling and recording in response to the acoustic shock waves at a minimum of one hundred kilocycles per channel.
Another aspect of this invention is a weather station coupled to the computer for automatically transmitting ambient atmospheric temperature data, wind velocity data and barometric pressure data to the computer, such weather data being subsequently processed by the computer as part of the iterative algorithm process of scoring the supersonic aerial projectiles.
Preferably, computer implementation of the iterative scoring algorithm includes processing the scoring data and the target data by indicating a quantitative and qualitative comparisons of the data to an operator by a visual display or by printout from a computer printer.
Also preferably, computer implementation of the iterative algorithm includes processing the comparison of calculated projectile scoring data with the target data by storing the quantitative comparisons in the computer memory for strafing trend analysis and archival use by the operator.
The process and apparatus of this invention accurately and rapidly displays, stores, and prints supersonic aerial projectile scoring data to an operator by: measuring supersonic aerial projectile acoustic shock waves received by an array of transducers, transmitting the transducer signals to an all-purpose digital computer, measuring weather data, and by implementing an iterative scoring algorithm to use the signal data and the weather data to iteratively calculate scoring data. The apparatus compares the scoring data to target data from the strafe target and indicates the quantitative and qualitative comparison of the data to the operator by display or printout.
One object of this invention is to provide a process and apparatus for scoring supersonic aerial projectiles that uses measuring the time-differences of arrival off the acoustic shock waves propagated by the projectiles at an array of at least six transducers to calculate scoring data.
Another object of this invention is to calculate and indicate the impact points (or nearest point of approach) of the projectiles on a strafe target for both on-target and off-target projectiles.
An additional object is to provide a scoring apparatus that does not have a defined non-tactical scoring area fixed at the location of a transducer, but instead has a scoring area selectable by the operator to conform to the actual physical location and shape of the strafe target.
A further object is to provide a process and apparatus that does not use fixed projectile calibers and signal parameters to calculate projectile scoring data.
An object of this invention is to automatically sample ambient atmospheric temperature and wind velocity data, and process this data by the computer implemented scoring algorithm, to improve projectile scoring accuracy.
Still another object is to estimate the firing range of the strafe aircraft by the computer-implemented scoring algorithm.
Yet another object of this invention is to indicate to the operator complete projectile scoring data, including projectile velocity, projectile dive angle, projectile heading angle, estimated strafe aircraft firing range and projectile burst patterns (e.g., physical patterns of impact of the projectiles upon a strafe target).
Still other objects of the present invention will become readily apparent to those skilled in this art from the following description of the invention, wherein only the preferred embodiments of the invention is disclosed, simply by way of illustration of the best mode contemplated of carrying out this invention. As will be realized, the invention is capable of other and different embodiments and its several details are capable of modifications in various obvious respects, all without departing from the invention. Accordingly the drawings and description are to be regarded as illustrative in nature, and not as restrictive.